Piston shoe construction



y 1969 R. E. RAYMOND 3,455,585

PISTON SHOE CONSTRUCTION Filed Dec. 1, 1965 2 Sheets-Sheet 1 I :s S

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ROBERT E.RAYMOND 3 (0 BY AT TORNEYS July 15, 1969 R. E. RAYMOND PISTON SHOE CONSTRUCTION z Sheets-Sheet 2 Filed Dec. 1, 1965 m T N E V m ROBERT E. RAYMOND JZZ/ ATTORNEYS 3,455,585 PISTON SHOE CONSTRUCTION Robert E. Raymond, Zanesvillc, Ohio, assignor to International Basic Economy Corporation, New York, N.Y., a corporation of New York Filed Dec. 1, 1965, Ser. No. 511,291 Int. Cl. F16c 11/06; F16s 27/02; B25g 3/38 US. Cl. 28721 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a piston construction for hydraulic machines and particularly to an improved piston shoe means that is mounted on a ball shaped piston foot and adapted to engage the cam that actuates the piston. The piston shoe means includes components that continuously take up operational wear by urging a segmented annular bearing radially inwardly against the side of said ball shaped piston foot.

The present invention relates generally to hydraulic machines and particularly to a novel piston shoe construction for engagement with the drive shaft cam of a pump or fluid motor.

In general the novel piston shoe construction comprises a metal encased piston shoe means formed of low friction material and mounted on a ball-shaped piston foot. The piston shoe means includes a novel multiple segment ring bearing and retaining cap means disposed in overlying relationship with the upper portion of the piston foot and each include tapered surfaces which engage one another such that vertical force in a downward direction urges the multiple segment bearing in towards the piston foot.

In accordance with the present invention the novel construction of the piston shoe means includes a multiple segment ring hearing which is constantly urged into engagement with the piston foot to take up any clearance or backlash and to compensate for wear between component parts over long periods of operation.

As another aspect of the present invention, the multiple segment ring bearing is covered by a continuous metal retaining ring which locks it in engagement with the piston foot.

As another aspect of the present invention, a novel piston and piston shoe construction is provided wherein each piston incorporates a spherical foot portion provided with a composite shoe means including socket forming components formed of low friction material, and a metal casing that not only reinforces the socket forming components against laterally directed tensil stresses, but also serves to retain the components in assembled relationship on the spherical piston foot.

As another aspect of the present invention, the novel piston and piston shoe construction is used in combination with a novel yoke formed of low friction material.

It is therefore an object of the present invention to provide a novel piston shoe construction which includes a multiple segment bearing ring constantly urged into engagement with the piston foot and which takes up any clearance or backlash between the component parts. Further, the bearing surfaces are constantly urged together to compensate for wear between the engaging parts over long periods of use.

It is another object of the present invention to provide a novel piston shoe construction wherein the multiple segment ring bearing is locked in place and covered by a continuous metal retaining ring.

It is another object of the present invention to provide a novel piston shoe construction that includes components formed of low friction material which are retained in asnited States Patent sembled relationship by a metal casing that also serves to prevent deformation and fracturing of the components under laterally directed tensil stresses.

It is another object of the present invention to provide a novel piston shoe construction that eliminates the need for high pressure lubrication in the hydraulic machine and which further will not gall when abrasive substances are encountered between the shoe and the cam means that drives it.

It is still another object of the present invention to provide a novel piston shoe construction that eliminates the need for holding close tolerances in the fitting of the drive components of a hydraulic machine.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a pre ferred form of embodiment of the invention is clearly shown.

In the drawings:

FIG. 1 is aside elevational sectional view of an axial type pump in which pistons and piston shoes constructed in accordance with the present invention are incorporated, the section being taken along a vertical plane through the centerline of the pump;

FIG. 2 is an exploded perspective view of the piston and piston shoe construction incorporated in the pump shown in FIG. 1;

FIG. 3 is a side elevational view, partially in section, of the piston and piston shoe construction shown in FIG. 2;

FIG. 4 is a plan view of a piston return yoke used in combination with the piston and piston shoe construction of FIGS. 2 and 3; and

FIG. 5 is a side sectional view of the piston return yoke of FIG. 4, the section being taken along the line 66 of FIG. 4.

Referring in detail to the drawings, FIG. 1 illustrates an axial piston pump of the type described in my copending application Ser. No. 167,030 filed Ian. 18, 1962, and now Patent No. 3,221,564 and therefore for simplification will not be described in detail herein.

In general, the pump of FIG. 1 comprises a housing means indicated generally at 20 which includes front and rear casing portions 22 and 24 joined together at confronting surfaces 26 and 28.

Rear casing portion 24 includes a plurality of openended circumferentially spaced bores that form cylinders 30 that receive a plurality of pistons indicated generally at 32.

The end of each cylinder 30 is closed by a reaction plug indicated generally at 34 that forms an outlet valve c-artridge and includes a recess 36 containing an outlet ball check valve 38, the end of recess 36 being closed by a threaded plug 40 that is crewed into a threaded bore 44. Plug 40 is provided with an axial outlet passage 42.

Reaction plug 34 further includes a plurality of radially extending outlet passage 46 that connect valve recess 36 with an annular groove 48 in the plug that in turn communicates with an annular manifold passage 30, the latter being core molded in rear casing portion 24.

Out-let check valve 38 is biased against an outlet valve seat 52 on the end of plug 40 by a compression spring 54, the latter being provided with a guide pin 56.

With continued reference to FIG. 1, each of the pistons 32 includes a spherical foot portion 76 on which is mounted a piston shoe means indicated generally at 80. The shoe means 80 rides on an inclined drive surface 82 of a cam means 84 that is keyed to a drive shaft 86 at a key 88, the cam means being retained on the shaft by a nut 90.

Shaft 86 is rotatably mounted in front casing portion 22 by conventional tapered roller bearings 94 and 96 that are pressed into recesses 98 and 100, said bearing being disposed in back to back relationship.

The front end of shaft 86 is provided with a wiper type seal assembly 102.

Pressurized oil from annular manifold is delivered to the load, not illustrated via outlet passage 116 that is formed in a subplate mounting block 110, the latter being bolted to front casing portion 22.

With reference to FIGS. 1, 4, and 5, the piston means 32 are returned to the bottom of their strokes by a yoke indicated generally at 124, said yoke being molded from low friction resinous material such as nylon or the like.

Yoke 124 includes an integrally molded spherical central socket 125 for receiving a spherical bearing portion 127 on the end of an axially shiftable yoke driving member 136, the later being mounted in a bore 129 in rear casing portion 124. Driving member 136 is constantly urged against yoke 124 by a compression spring 138 the ends of which are centered by spring positioners 140 and 142.

As shown in FIG-S. 4 and 5, the periphery of yoke 124 is provided with a plurality of circumferentially spaced holes 131 that are large enough to permit free oscillation of neck portions 128 of piston means 32.

The periphery of yoke 124 further includes a plurality of piston shoe mounting recesses 133 that are shaped to form snugly fitting sockets for the tops of the piston shoe means indicated generally at 80 in FIGS. 1 and 3.

Reference is next made to FIG. 3 which illustrates in detail a piston and piston shoe constructed in accordance with the present invention.

The shoe means 80 of composite construction and includes a lower bearing portion 144 that forms an upper spherical surface 146 for receiving spherical piston foot 76 and a lower bearing surface 148 that engages the upper surface 82 of cam means 84.

With continuted reference to FIGS. 2 and 3, a multiple segment ring formed by segments 150 and 152 comprises an upper bearing portion of shoe means 80.

Segments 150 and 152 include spherical surfaces 154 that conform with the upper portions of ball-shaped piston foot 76 and a pair of tapered surfaces 156 and 158, the upper tapered surfaces 156 being formed on a rib or shoulder portion and the lower tapered surfaces being formed on the base portion of each segment.

A continuous retaining ring 160, preferably formed of metal, covers segments 150 and 152 and includes tapered surfaces 162 and 164 which engage tapered surfaces 156 and 158 respectively such that a gap or clearance 166 exists between segments 152 and 150 and ring 160, as best seen in FIG. 3.

A metal casing, indicated generally at 170, surrounds shoe means 80, and includes an upper edge 172 that is crimped over retained ring such that ring 160 locks segments 150 and 152 in place and an inner shoulder 174 that surrounds a recess 176 of reduced diameter provided on the lower end of lower bearing portion 144.

Lower bearing portions 144, multiple segments 150 and 152 are formed of lower friction material, preferably nylon or the like, whereby galling is eliminated between the pivotal bearing portions in metal ball-shaped piston foot 76 and also between lower bearing portion 144 and metal cam means 84.

It will be understood that the above mentioned nylon to metal bearing surfaces, although under relatively heavy axial loads, will not gall or cause failure when metal chips or other foreign particles are encountered.

The operation of the pump of FIG. 1 as a whole is described in detail in the previously mentioned patent application Ser. No. 167,030, and therefore for simplification only the operation of the piston and return yoke involving the piston shoe means 80 will be described in detail herein.

When shaft 86 is driven by a prime mover, not illustrated, rotation of cam means 84 exerts axial forces on pistons 32 and causes reciprocation in cylinders 30.

On the return stroke of each piston 32, FIG. 1, a vertical or axially directed force is exerted on retaining ring 160 by the surface of shoe mounting recess 133 of yoke 24 whereby ring 160 axially urged against ring bearing segments 150 and 152.

Engagement between the respective tapered surfaces 156, 158, 162 and 164, forces multiple ring bearing segments 150 and 152 radially inwardly towards piston foot 76 and thereby maintains engagement between the spherical surfaces 154 of bearing segments 150 and 152 and the outer bearing surface of piston foot 76.

The original dimension of the tapered surfaces determine the amount of clearance 166 that exists. The clearance or gap 166 that exists between the bottom of the interior level surface on ring 160 and the top of the interior level surfaces of segments 150 and 152 represents the amount of clearance or backlash that may be taken up between the spherical surfaces 154 and piston foot 76.

It will be understood that wear between surfaces 154 and foot 76 over long periods of operation is compensated for by the novel construction of shoe means 80 as spherical bearing surfaces 154 are being urged inwardly by the action of the double tapered surfaces on ring 160 and segments 150 and 152 respectively.

When the high axial stresses are imposed on the shoe means 80, the resinous lower bearing members 144 have the advantageous characteristic of possessing high strength under compression. These lower bearing portions 144 have the undesirable characteristic of being relatively Weak when subjected to tensile stresses. Since the spherical piston foot 76 is axially forced into the hemispherical socket 146 of the lower bearing portion, the lower bearing portion is subjected to radially directed tensile forces and since the low friction resinous materials such as nylon are relatively weak under tension, the metal casing 160 confines bearing portion 144 against radial deformation and rupture.

I claim:

1. In a piston construction for engagement with the cam means of a hydraulic machine, the combination of a piston shoe means mounted on a ball-shaped piston foot, said shoe means including a lower bearing portion for engagement with said cam means; an upper multiple segment ring bearing overlying the upper portion of said ball-shaped piston foot; retaining means in overlying force transmitting relationship with said ring bearing, said retaining means and ring bearing including at least one pair of tapered surfaces in force transmitting relationship with each other whereby downward pressure on said retaining means forces said segments of said ring bearing inwardly against said piston foot; and a casing for retaining said lower bearing portion, ring bearing, and retaining means in assembled relationship.

2. In a piston construction for engagement with the cam means of a hydraulic machine, the combination of a piston shoe means mounted on a ball-shaped piston foot, said shoe means including a lower bearing portion for engagement with said cam means and provided with a side wall having a recess; a casing including a lower portion provided with an inner shoulder disposed in said recess, the upper portion of said casing including an upper shoulder; a multiple segment ring bearing overlying the upper portion of said piston foot; and retaining means mounted between said upper shoulder and said ring hear-- ing and including means for urging said ring bearing radially inwardly.

3. A piston construction for engagement with the cam means of a hydraulic machine comprising in combination, a piston shoe means mounted on a ball-shaped piston foot, said shoe means including a lower bearing portion for engagement with said cam. means; an upper multiple segment ring bearing overlying an upper portion of said ballshaped piston foot and including a base portion provided with a first tapered surface and a shoulder portion provided with a second tapered surface; retaining means disposed over said ring bearing and including a first tapered surface engaging said first tapered surface on said base portion and a second tapered surface engaging said second tapered surface on said shoulder portion; and a casing for said lower bearing portion, ring bearing and retaining means, said casing including means for retaining said lower bearing portion in said casing.

4. In a piston construction for engagement with the cam means of a hydraulic machine, the combination of a casing surrounding a piston shoe means mounted on a ball-shaped piston foot, said shoe means including a lower bearing portion for engagement with said cam means and an upper ring-shaped bearing overlying an upper portion of said ball-shaped piston foot, said ring shaped bearing including a base provided with an upraised shoulder, said base and said shoulder each including a tapered surface; and a circular retaining member overlying said ring-shaped bearing and including tapered surfaces in force transmitting realtionship with said tapered surfaces on said ring-shaped bearing.

5. In a piston construction for engagement with the cam means of a hydraulic machine, the combination of a piston shoe means mounted on a ball-shaped piston foot, said shoe means including a lower bearing portion for engagement with said cam means; a multiple segment ring bearing overlying an upper portion of said ball-shaped piston foot, each of said segments of said ring bearing including at least one tapered surface; a casing surrounding said lower bearing portion and ring bearing; and a circular retaining member overlying said segments of said ring bearing and axially movable in said casing, said retaining member including at least one tapered surface in force transmitting engagement with said tapered surfaces on the segments of said ring bearing for urging said segments radially inwardly toward said piston foot when said retaining member is forced axially against said segments.

6. In a piston construction for engagement with the cam means of a hydraulic machine, the combination of a piston shoe means mounted on a ball-shaped piston foot, said shoe means including a lower bearing portion for engagement with said cam means; a multiple segment ring bearing overlying an upper portion of said ballshaped piston foot, said ring bearing including first and second tapered surfaces; a circular retaining ring mounted over said ring bearing and including third and fourth tapered surfaces in force transmitting engagement with said first and second tapered surfaces, the dimensions of said tapered surfaces being predetermined such that a clearance exists between certain portions of said ring bearing and said retaining ring; and retaining means for mounting said piston shoe means and said retaining ring together.

7. A piston construction for engagement with the cam of a hydraulic machine comprising, in combination, a lower bearing portion provided with a lower surface for engaging said cam means and an upper annular surface extending outwardly from a ball-shaped piston foot; an upper bearing means including a plurality of segments surrounding said ball-shaped piston foot, said segments including lower surfaces in inwardly slideable engagement with said upper annular surface of said lower bearing portion; a casing for said lower bearing portion and multiple segment bearing means; and means axially movably mounted in said casing and engaging said segments for urging said segmets radially inwardly along said annular surface and against the outer side surface of said ball-shaped piston foot.

References Cited UNITED STATES PATENTS 2,638,850 5/1963 Ferris 287-21 2,880,042 3/1959 Budzich 74-60 3,038,459 6/ 1962 Schmid.

3,060,712 10/1962 Sisson 74-60 XR 3,180,159 4/1965 Girodin 74-60 3,212,483 10/1965 Balzer 92187 XR 3,221,564 12/1965 Raymond 103-162 XR 3,272,541 9/ 1966 Latzen.

CARL W. TOMLIN, Primary Examiner ANDREW V. KUNDRAT, Assistant Examiner US. Cl. X.R. 

